The present invention concerns improvements to chromatography apparatus and in particular to columns containing a porous packing.
It is known in the prior art to utilize tubular columns presenting a piston or other sliding body to ram or compress the packing in a chamber between this piston and a fixed bottom or detachable cover; the piston being displaced by a jack or other actuating device associated with the piston rod.
The present invention is aimed at facilitating the operations concerned and simplifying the material required for their achievement in order to ensure improved conditions during the successive steps involved, which comprise filling the column with the packing, compressing the same, the chromatography properly speaking, while maintaining the compression and, furthermore, the final phase consisting either in returning to initial conditions, or in emptying the column especially with a view to changing the packing.
French patent No. 72 07278 discloses chromatography apparatus constituted by a column intended to contain a support made of adsorbing material, the column comprising:
a tube provided at one of its ends with a fluid-permeable (i.e. permeable to liquids or gases) cover and communicating with the outside; PA1 a body sliding along the axis of the tube and consisting of a piston formed, on the one hand, of a head constituted by a porous plate which is permeable to fluids and which exerts to exert a pressure inside the tube, and, on the other hand, a piston rod controlling the displacement of the piston head. PA1 In the one hand, it requires a piston rod in order to transmit to the piston head the displacement necessary to ensure the expulsion of the liquid forming the suspension of the particles of which the packing is formed. This rod must have a length at least equal to the length of travel or stroke of the piston and thus requires a length that is practically equal to the length of the column, if it is desired to utilize the column only on a small portion of its total length. Indeed, such a stroke of the piston (which would be in certain cases about 3 to 4 meters) requires below the column a space sufficient to ensure this stroke; PA1 on the other hand, when, following extended use of a column, a slight compression of the packing occurs in the column due to contraction, crushing or weak dilution of the adsorbent mass leading to a loss of resolution power of the column, it is no longer possible to compensate such undesirable compression if the piston stroke is limited to one portion of the column, so that it is necessary to open the column and add a further amount of adsorbent material; this is not simple to do and can become necessary rather often, not to mention the fact that in the case of thin packings smaller than the size of the adsorbent mass particles, this can prove to be impossible.
This French patent indicated that the apparatus so disclosed exerts a pressure on the particles intended to constitute the adsorbent support. Such a pressure can be exerted during the filling of the column, after a suspension of particles of the material has been introduced into the tube, in order to thus cause the liquid to pass through the porous plates and to compress the particles between the sliding body and the cover, and thus to form the adsorbent support necessary for exactly operating the chromatography process, namely to prevent poor homogeneity of the packing which constitutes a serious defect in the chromatography columns.
In fact the apparatus described in this French patent presents several drawbacks:
The present invention concerns an improved apparatus allowing to overcome the drawbacks of the known apparatus and especially of the apparatus according to the above-mentioned French patent.
In fact, the chromatography apparatus according to the invention can be utilized with widely variable volumes of adsorbent mass without requiring the availability of a large lost volume below or above the column in order to ensure the piston stroke. Furthermore, the novel apparatus does not require heavy investment in equipment having different dimensions, since a single column of considerable length can be adapted to any length required. Furthermore, the problems of sealing and maintaining this sealing are easier to overcome.
The present invention provides an improved chromatography apparatus or column constituted by a tube, one portion of which constitutes a chamber intended to contain a packing or adsorbent material mass, this tube comprising at each of its ends an end wall presenting communicating means for communication with the outside and, on the other hand, at last one sliding body being longitudinally displacible within the cylinder and having connecting means for connection with a duct communicating with the outside, wherein the sliding body is displaced by the pressure exerted by a pressurized fluid injected into an enclosure formed between the sliding body and the end wall opposite facing the chamber containing the packing.
Furthermore, the means provided to produce the pressure in the enclosure include a hydraulic circuit comprising, on the one hand, a conduit connecting said enclosure to an elution agent reservoir and the portion of the tube intended to contain the packing, the conduit associated to a pump and a first valve, the circuit also comprising, on the other hand, a shunting conduit possibly comprising a second valve, and connecting the enclosure to the input conduit at a point located between the pump and the first valve.
Two calibrated flap valves are also provided, respectively positioned on the input conduit between the point and the first valve, and on the shunting conduits between the point and the enclosure.
Furthermore, the shunting conduit comprises between the enclosure and the flap valve an evacuation conduit for the hydraulic fluid, which conduit comprises a third valve. The sliding body or piston is crossed through, by connecting means consisting of a conduit communicating with the atmosphere, this conduit being a flexible conduit the length of which is at least equal to the possible stroke of the sliding body.
Two sliding bodies can also be provided, each of them being disposed at a respective one of the ends of the above-mentioned tube, a connection being established between the two enclosures.
Other various arrangements can be envisaged, and in particular, the following:
The surface of the sliding body intended to be opposed to the packing is larger than the surface of the sliding body intended to be in contact with the packing.
The sliding body comprises means of connection with the means for communicating with the atmosphere which are provided in the end wall, these communicating means being connected to a supply circuit of the flowable phase intended to be used for the elution.
The pressure intended to be exerted in the enclosure is produced by means of the elution fluid and the additional pressure results from the relative calibration clearances of the calibrated flap valves placed on the hydraulic circuit and the shunting conduit.
In order to cause the piston or sliding body to be returned after the chromatography step proper, it is possible to reverse the flow direction of the fluid between the pump and the enclosure utilized for the propulsion by a set of valves and reversal channels.
In order to prevent the packing particles from tending to be introduced between the piston and the tubular column, the fluid is brought to the piston and enters the chromatography chamber by inlets disposed along the periphery of the piston, whereby the particles tend to spread out from the wall of the tube immediately adjacent to the piston.
The piston can also comprise a device sealing these inlets during the chromatography step proper, for example, beyond a selected pressure threshold.
When two pistons having two sections are provided, these may be constituted by two elements able to be repaired when one of them reaches at the end of the stroke, so as to modify the pressure exerted on the packing. Therefore, by limiting the stroke of the large-diameter portion, the pressure is only exerted on a smaller section or area during the chromatography step. It is also possible to utilize pistons double-acting or simultaneously and/or successively acting pistons. It can be envisaged, too not to use simple sealing caps or covers for enclosing the column, but heads containing the pistons and their supply conduits, which considerably simplifies assembly and disassembly.
Another object of the present invention is to provide a chromatographic separation process consisting essentially in positioning the packing, of exerting the fluid pressure in order to compress the same, continuing to exert a pressure necessary for maintaining the compression during the chromatography step proper, carrying out the elution step, then possibly in modifying the pressure either to return to the initial conditions, or with a view to changing the packing.